This invention relates generally to gas turbine engines and more particularly, to methods and apparatus for cooling gas turbine engine rotor assemblies.
At least some known rotor assemblies include at least one row of circumferentially-spaced rotor blades. Each rotor blade includes an airfoil that includes a pressure side, and a suction side connected together at leading and trailing edges. Each airfoil extends radially outward from a rotor blade platform. Each rotor blade also includes a dovetail that extends radially inward from a shank extending between the platform and the dovetail. The dovetail is used to mount the rotor blade within the rotor assembly to a rotor disk or spool. Known blades are hollow such that an internal cooling cavity is defined at least partially by the airfoil, platform, shank, and dovetail.
During operation, portions of the airfoil of the blades are exposed to higher temperatures than other portions of the blades. Over time, such temperature differences and thermal strain may induce thermal stresses in the blade. Such thermal strains may induce thermal deformations to the airfoil, for example, local creep deflection, and may cause other problems such as airfoil low-cycle fatigue, which may shorten the useful life of the rotor blade.
To facilitate reducing the effects of high temperatures within at least some known rotor blades, at least some of the rotor blade airfoils include a trailing edge slot and a cut back pressure-side wall with the slot divided into evenly spaced channels which discharge a film of cooling air over the exposed back surface of the airfoil. However, because of temperature differences at different points along the trailing edge, the air from the evenly spaced slots does not cool the trailing edge enough to remove the temperature differential between different points along the trailing edge of the airfoil.